by , Ranger
Greg Dodge is a professional naturalist as well as a writer, videographer and producer of natural history DVDs. His images have been used in various TV productions, museum displays, and corporate videos. Above all, he has a fascination and passion for all things natural.
Stop by and say hello Tuesday thru Saturday in Explore the Wild, Catch the Wind, or on the Dino Trail.

A Busy Time for Arthropods

May 15th, 2009

A large millipede (about 4 inches) was seen walking across the path in front of the Ornithopter. My best guess is that it was Narceus americanus. N. Americanus is the classic, round-in-cross-section form of millipede that’s most often encountered in our area. The other locally common millipede is about two inches in length, has a flattened, black body and yellow legs.

All insects have six legs. Beyond that simple fact, the incredible array of shapes, colors and life styles of insects is staggering. Just when you think you’ve seen the most beautiful, the most bizarre, or the most peculiar behavior, along comes something more beautiful, more bizarre, or more eccentric in behavior. The good thing about all of this is that you don’t have to go to the Amazon to see these strange creatures — they’re right here, all around you. You just have to look!

Dragonfly activity continues to increase. Surprisingly, I saw the first Lancet Clubtail of the season on May 9th; in fact, it was the first of this species that I’ve ever seen at the Museum. It’s odd that I hadn’t seen one at the Museum previously. While most clubtails prefer stream habitats, Lancet Clubtails are more often found at ponds. The Wetlands is a good example of a pond habitat. What’s more, these little clubtails are early season fliers. We’re now well into spring, so I would have expected to see a Lancet Clubtail much earlier in the season.

Two other dragonflies, Carolina Saddlebags and Twelve-spotted Skimmer, have also made the first-of-year list. Both were seen in the Wetlands on May 9 and 10, respectively.

If you get down low and look closely at the vegetation that lines the Explore the Wild/Catch the Wind loop, you may see a very small insect with long, folded hind legs sitting atop a blade of grass. Many tiny grasshoppers have recently hatched out. In most cases, grasshoppers lay their eggs in the soil, the eggs overwintering where they were deposited. The young hatch out the following spring as nymphs and through a series of progressive molts attain their adult form. So, get down and have a look and see if you can spot one of these little nymphs!

With the daisies in Catch the Wind at their peak, there have been many opportunities to peer into the lives of insects that you might otherwise have overlooked. One such insect is the White-margined Burrower Bug (Sehirus cinctus). It looks like a tiny black stink bug with a shiny back. Of the burrower bugs, this is the one you’re most likely to come across. Most burrower bugs spend a good part of their time below ground. The only photos that I have of this tiny insect is of one sitting on the railing of my front porch, but you can see many fine representations of them here.

Lady Bugs, or Lady Beetles, are currently present in all of their forms, larva, pupa, and adult. The larva and adults may be seen on the daisies themselves, the pupa more likely on a leaf of a daisy or other nearby plant.

Another beetle found on the daisies was a Clover Stem Borer (languria mozardi). You guessed it, it bores into clover, but not exclusively. It has also been reported to do damage to wheat and other crops. Again, I don’t have an image to show you but you can get a quick look here. They’re about 5 or 6 mm in length so, as I keep saying, it may require getting down to flower level to see them.

gd_5_1_09zeloA long-horned beetle that’s often seen at flowers is the Zebra Longhorn (Typocerus zebra). The one pictured was sitting atop a daisy in front of the Ornithopter on 9 May. The larvae bore into pine trees.

An Eyed Elater (Alaus oculatus), or Eyed Click Beetle, flew into Animal Keep Larry while he was finishing up his Meet the Keeper Program in front of the Red Wolf Exhibit on 8 May. Adeptly captured by Larry, the large, strange-looking click beetle was seen by several Museum guests before it was released (see Eyed Elater, Explore the Wild Journal, May 1-15, 2008). The timing of this beetle’s appearance this year matches its emergence last year, almost to the day. Just like the blooming of flowers, or the migrations of birds, insects usually appear at the same time each year. Curiously, I’ve not seen an Eyed Elater on the Explore the Wild/Catch the Wind loop in any month other then May. They’re still in the area, but apparently more difficult to find.

gd_5_1_09bessAnother large beetle often seen wandering around during spring is the Bess Beetle, or Horned Passalus (at one time they were called Patent Leather Beetles because of their very shiny exoskeleton, as seen in the image at left). I found two of these large, shiny beetles on the path around the Explore the Wild/Catch the Wind loop on the 10th of May. They’re common in our area. I’ve often found them plodding across hiking trails and roads during spring. However, they can be found throughout the year. If you have a wood pile or large rotting logs on your property, you probably have a colony of these beetles as neighbors (colonial behavior is unusual in beetles. Look it up). You may have to dig into the log to see them though.

On the morning of May 8, while walking along the path on my way to the Ornithopter, I noticed many small black specks on the pavement below. This could only mean one thing: caterpillars feeding in the trees above. The black specks were frass (caterpillar poop). Overhanging the path directly above me were several branches of an elm tree, one of the favored food plants of Mourning Cloak caterpillars. Some of the branches were devoid of leaves — there were definitely caterpillars at work here. A little further back up the branch, toward the trunk, were 30-40 large, red-spotted, black caterpillars munching away on the fresh, green elm leaves.

The first Hackberry Emperor of the season was seen on the 9th day of the month. These medium-sized, brown butterflies have a tendency to land on people, so don’t be surprised if you get buzzed by one of them while walking through Catch the Wind.

gd_5_1_09gbsfOn May 10th, a fly that I’d never seen before landed on one of the daisies in front of the Ornithopter. It was a Golden-backed Snipe Fly (Chrysopilus thoracicus). They’re predatory flies. I don’t know exactly what they prey upon but I’ve seen a photo of one of these flies with what looks to be a tiny bee or fly and have read that they may prey on aphids.

Male Golden-backed Snipe Flies have larger eyes and narrower abdomens than the females. This looked like a male (image at left). Although it visited many flowers in the area and sat for long periods each time it perched, the fly didn’t do much else. Once it alighted, it just sat motionless on the flower. Neat looking fly.

gd_5_1_09brac1By far, the most interesting insect encounter of the period was with a tiny wasp making visits to the daisies now in bloom. Brachonid wasps are small parasitic wasps that lay their eggs on or into the bodies of other insects. If you’ve ever seen a Tobacco or Tomato Hornworm with tiny white sacs hanging from its sides, you’ve seen a brachonid wasp, or rather the cocoons of a brachonid wasp. In the case of your hornworm, a wasp would have oviposited (laid eggs) within the big, juicy caterpillar’s body. The larvae would have hatched from those eggs, fed on the caterpillar from within, grown and migrated to the outside of the body, spinning tiny silken cocoons (the white sacs) in the process. The larvae would now be pupating within those cocoons. One pupa per cocoon. If you had watched the cocoons carefully, and not smashed the caterpillar because it was eating your tomato plant to shreds, you would have, in time, seen the tops of those little cocoons chewed off (leaving a small hinge on one side), pop open and tiny wasps crawl out, dry off, rub their wings with their little legs and fly off. You would have then seen a brachonid wasp, many brachonid wasps.

gd_5_1_09brac2If you don’t have the time, the inclination, or the patience to wait for all of the above to happen, don’t sweat it — I did it for you. Go here, scroll down and click on “View Sample.” The wasps in the video that you will see (or have just watched) are a different species than the ones on the daisies in Catch the Wind, but the idea is the same.

Back to the daisies. Over the past few weeks I’ve been seeing brachonid wasps (I’m not 100 percent sure that they are brachonid wasps, but reasonably sure) fly about and land on the daises in Catch the Wind. Sometimes a wasp would feel around the flower disc and fly off. Other times, the wasp would busily “smell” the disc with its antennae, rear up and insert its long ovipositor (that long, thin projection in the rear of the wasp in the images at left) down into the seed disc of the flower. What’s going on here!

There had to be more to this than a wasp laying eggs on a flower, but what was it doing? How would the wasp larva feed itself? On seeds? No, there had to be something else going on. This was a parasitic wasp. I knew that much. It sounded reasonable to me that there would be some kind of insect or insect larva down below the surface that these wasps could sense with their antennae, locate with their ovipositor and lay eggs on. After all, there are many other insects visiting the flowers during the day. Maybe a beetle or weevil lays eggs on daisies and the wasps parasitize them? I’ve certainly seen many Lady Beetle larvae on the flowers. But they’re large, easily seen, and spend their time out in the open hunting down aphids.

Robin, from the Butterfly House, took one of the flowers back to the Butterfly House. After viewing the flower’s disc under magnification she reported seeing many thrips larvae within the disc. Are the wasps laying their eggs on thrips? Sounds plausible to me. But, I’m still investigating and will report back any findings in the future.

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